Automatic insulation resistance testing apparatus

1. An apparatus for automatically measuring and recording insulation resistances of a multi-conductor cable comprising:

power supply source;

input measuring means;

output measuring means;

input relay controlled contacts;

output relay controlled contacts;

relay controller; and

computer,

wherein the computer transmits instructions to the relay controller to set the position of input relay controlled contacts and output relay controlled contacts;

wherein the computer receives digital messages from the input measuring means;

wherein the computer receives digital messages from the output measuring means;

wherein the digital messages received from the input measuring means and output measuring means comprise values of measured variables;

wherein the computer records an input measured variable value and an output measured variable value for each combination of input relay controlled contact position and output relay controlled contact position;

and wherein the computer determines insulation resistance values from the recorded values of measured variables.

2. The apparatus of the claim 1 wherein the input relay controlled contacts comprise 10 or more contacts and the output relay controlled contacts comprise 10 or more contacts.

3. The apparatus of claim 1 wherein the input measuring means consists of a voltage measuring means comprising computer interface connection and the output measuring means consists of a voltage measuring means comprising computer interface connection.

4. The apparatus of claim 3 wherein computer interface connections are in accordance with IEEE specification 488 for computer communication interfaces.

5. The apparatus of claim 1 wherein the relay controller means comprises a programmable logic controller further comprising controller instructions for selectively closing contacts of the input relay controlled contacts and the output relay controlled contacts in accordance with instructions received from the computer.

6. The apparatus of claim 1 wherein the relay controller means comprises a distributed control system further comprising controller instructions for selectively closing contacts of the input relay controlled contacts and the output relay controlled contacts in accordance with instructions received from the computer.

7. The apparatus of claim 1 wherein a measured pair of input measured variable value and an output measured variable value is recorded for each combination of 2 conductors of the multi-conductor cable.

8. The apparatus of claim 7 wherein the input measured variable is a voltage value and the output measured variable is a voltage value.

9. The apparatus of claim 1 wherein the multi-conductor cable comprises ganged single insulated conductors.

10. The apparatus of claim 1 further comprising a fire test chamber.

11. An apparatus for automatically measuring and recording insulation resistances of a multi-conductor cable comprising:

power supply source;

input measuring means;

output measuring means;

input switching unit;

output switching unit; and

control unit/data logger,

wherein the control unit/data logger transmits instructions to set the position of input switching unit contacts and transmits instructions to set the position of output switching unit contacts;

wherein the control unit/data logger receives digital messages from the input measuring means:

wherein the control unit/data logger receives digital messages from the output measuring means;

wherein the digital messages received from the input measuring means and output measuring means comprise values of measured variables;

wherein the control unit/data logger records an input measured variable value and an output measured variable value for each combination of input switching unit contact position and output switching unit contact position; and wherein the control unit/data logger determines insulation resistance values from the recorded values of measured variables.

12. The apparatus of claim 11 wherein the input switching unit contacts comprise 10 or more contacts and the output switching unit contacts comprise 10 or more contacts.

13. The apparatus of claim 11 wherein the input measuring means consists of a current measuring means comprising control unit/data logger interface connection and the output measuring means consists of a current measuring means comprising control unit/data logger interface connection.

14. The apparatus of claim 11 wherein the control unit/data logger, the input switching unit and the output switching unit are integrated into a single programmable logic controller device.

15. The apparatus of claim 11 wherein the control unit/data logger, the input switching unit and the output switching unit are integrated into a single distributed control system device.

16. The apparatus of claim 11 wherein the control unit/data logger, the input switching unit and the output switching unit are integrated into a single data acquisition and control system device.

17. The apparatus of claim 11 wherein a measured pair of input measured variable value and an output measured variable value is recorded for each combination of 2 conductors of the multi-conductor cable.

18. The apparatus of claim 17 wherein the input measured variable is a current value and the output measured variable is a current value.

19. The apparatus of claim 11 wherein the mult-conductor cable comprises ganged single insulated conductors.

20. The apparatus of claim 11 further comprising a fire test chamber.

21. A method of automatically determining insulation resistances of a multi-conductor cable, the method comprising the steps of:

connecting a multi-conductor cable to a power source;

automatically connecting an input voltage of higher value to one conductor of the multi-conductor cable;

automatically connecting an output voltage of lower value, in turn to each remaining conductor of the mult-conductor cable;

automatically measuring and recording an input measured variable and an output measured variable for each combination of automatic connecting to an input voltage and connecting to an output voltage; and

determining multi-conductor insulation resistances from the recorded values of input measured variable and output measured variable.

22. The method of claim 21 wherein the input measured variable and output measured variables comprise voltages measurements determined from electrical connections across ballast resistors of known values.

23. The method of claim 21 wherein measured pairs of an input measured variable value and an output measured variable value is recorded for each combination of 2 conductors of the multi-conductor cable.

24. The method of claim 21 wherein automatically measuring and recording of an input measured variable and an output measured variable occur while the multi-conductor cable is exposed to a fire test.